1. Field of the Invention
The invention relates to a metal bearing liner and an improved axial flow fan motor provided with the same.
2. Description of Related Art
Various types of office automation (OA) apparatuses have a large number of electronic circuits enclosed in the housing thereof, whereby heat may be generated by the electronic circuits giving a bad influence on some of electronic devices of the apparatus. The remarkable technical advancement of a microprocessor unit (hereinafter referred to as xe2x80x9cMPUxe2x80x9d) for a personal computer (PC) has been realized leading to a further improvement for higher-integration, higher respond speed and higher-functionality. On the other hand, the heat generated by the MPU has been continuously increased in its amount contrary to the fact that the housing space tends to be reduced in order to downsize the main body of the apparatus. Accordingly, it has become an important technical task to devise effective measures against heat.
An OA apparatus in general is provided with a ventilation hole formed on a side wall of the housing thereof, and an axial flow fan motor 21 (see FIG. 7) is provided on the back side wall of the ventilation hole (inside of the housing) in order to radiate the generated heat from the MPU to the outside of the housing. The axial flow fan motor 21 shown in FIG. 7 is one of the examples of the axial flow type fan motors wherein an impeller 23 rotates in a resin-made casing 22. As shown in FIGS. 7 and 8, a motor housing 24 is integrally formed with the casing 22 at the substantially center thereof, and a substantially cylindrical metal bearing liner 25 formed by an insert molding is set so as to stand at the center of the motor housing 24.
As shown in FIG. 7, the outer peripheral surfaces of a pair of bearings 26 are fitted and fixed on the inner peripheral surface of the bearing liner 25 in such a manner that a shaft 27 is rotatably supported by those bearings 26. Moreover, a motor yoke 29 is fixed to the shaft 27 through a zinc die-cast-made bush 28. The base portion 23a of the impeller 23 is fixed on the outer peripheral surface 29a of the motor yoke 29, and a magnet 34 is disposed on the inner peripheral surface 29b of the yoke 29. And, the shaft 27, the motor yoke 29, the impeller 23 and the magnet 34 constitute a rotary part.
Furthermore, as shown in FIG. 7, a stator 31 composed of a stator core 31a and stator wire 31b wound therearound is fitted on the outer peripheral surface 30 of the bearing liner 25. A PC board 32 composed of electronic circuits is provided beneath the stator 31. In the present axial flow fan motor 21, the PC board 32 controls the current to be supplied to the stator 31. A reference numeral 33 in FIG. 7 refers to a lead wire for supplying a power source current to the electronic circuits on the PC board 32.
The axial flow fan motor 21 thus structured is required to obtain a high cooling performance, a low current consumption, quietness, and a long life. Accordingly, the bearings 26 for supporting the rotary part are needed to reduce torque and noise and to elongate the life. Furthermore, the bearing liner 25 holding the bearings 26 is required to have a high roundness and cylindricality in its bearing fitting portions 35 (see FIG. 8) to which the outer rings of the bearings 26 are fitted. Consequently, the conventional bearing liner 25 has been formed by a cutting work in order to obtain a high accuracy. That is, the outer peripheral surface 30 has to be provided so as to form a ring-shaped groove 36 preventing the fall out of the bearing liner 25 and a knurl 37 preventing the rotation of the bearing liner 25. Such cutting work of the bearing liner 25 is intricate and requires frequent tooling change and many process, which increase the manufacturing cost of the bearing liner 25 resulting in the cost increase of the axial flow fan motor 21.
The present invention was made in light of the above, and it is an object of the present invention to provide a metal bearing liner and an axial flow fan motor provided with the same formed by an insert molding to the resin-made motor housing thereof. In the present invention, the metal bearing liner conventionally formed by a cutting work can be formed by a press work while maintaining a requisite accuracy so that the manufacturing cost of the metal bearing liner, that is, the cost of the axial flow fan motor is reduced.
For attaining the aforementioned object, according to the first aspect of the present invention, there is provided a metal bearing liner formed into a substantially cylindrical shape and performed for an insert molding to a resin-made motor housing, which has an inner peripheral surface to which a bearing for supporting a shaft of a rotary part is fitted, wherein the metal bearing liner is formed by sequentially performing a plurality of press processes over a progressive sheet material.
In the aforementioned structure, the metal bearing liner with a requisite accuracy can be obtained through the press work.
According to the second aspect of the present invention, a plurality of projecting portions for positioning the bearing are provided on the inner peripheral surface of the bearing liner.
In the aforementioned structure, the bearing can be positioned in the axial direction of the bearing liner.
According to the third aspect of the present invention, a flange is provided at the base portion of the bearing liner and a notch is disposed at a side edge of the flange.
In the aforementioned structure, because the insert molding is performed for the metal bearing liner to a resin-made motor housing, the flange can prevent the come out of the bearing liner and the notch can also prevent the rotation of the bearing liner.
According to the fourth aspect of the present invention, the insert molding is performed for the bearing liner to the motor housing by inpouring a resin into recesses formed on the back of the projecting portions.
In the aforementioned structure, it will be possible to perform the insert molding for the bearing liner to the motor housing, by which the resin inpours into the recesses of the bearing liner, so that the come out as well as the rotation of the bearing liner with respect to the motor housing can be prevented.
According to the fifth aspect of the present invention, there is provided the axial flow fan motor including the metal bearing liner formed into a substantially cylindrical shape and performed for the insert molding to the resin-made motor housing in such a manner that the bearing liner stands therein, in which the metal bearing liner is formed by sequentially performing a plurality of press processes over a progressive sheet material
In the aforementioned structure, the metal bearing liner can be formed through the press work (progressive press work) instead of conducting the conventional cutting work when performing the insert molding to the motor housing in the axial flow fan motor.